Description: (Applicant's Description) The Histopathology Laboratory provides Institute scientists with services for tissue processing (both cryo and paraffin), tissue sectioning, histochemical and immunostaining, and light microscopic examination of cells and tissues. The Service also provides consultation on matters related to immunostaining and histopathological evaluation of human and rodent organs, tissues, and cells. Transmission, scanning, and cryo-EM of tissues and cells are also offered. The Service also maintains common equipment, such as cryostat, microscopes, and in situ PCR apparatus for investigators' use. This Facility was started as a shared resource in the Fall of 1994. Currently the Facility supports a large number of projects including investigations on human tumors, experimental tumors in mice, experimental tumor treatments in mice, and the analysis of a large number of mutant mouse strains by routine histology, immunohistology, and EM.